I've never had this happen fever - my foot has a small "crack" between the ball below the big toe and the arch. Blisters near here - yes, cracks, not to my recollection. I noticed it before heading out to retrieve Monday. I was almost unnoticeable when running, just occasional weird angles might light it up. It's worse around the house.
I have a lengthy hike planned for Sunday or Monday, not sure if I should moderate because of it or just lotion/lotion/lotion and hope for the best.
Athletes Foot would be my medical opinion. Since I'm an engineer that shouldn't count for much however. Thick callouses can also crack which is why I file mine down weekly.